Method of and apparatus for replacing cutting implements in severing machines

ABSTRACT

Apparatus for replacing spent and/or damaged knives with fresh knives in a machine wherein semifinished rod-shaped smokers&#39; products are converted into cigarettes, filter mouthpieces or the like employs a knife holder, a locking device which can releasably clamp a knife in the holder, a preferably automated system for temporarily deactivating the locking device in order to allow for removal of a spent knife, and a conveyor system for introduction of a fresh knife into the holder subsequent to removal of the spent knife and prior to renewed activation of the locking device.

CROSS-REFERENCE TO RELATED CASES

[0001] The present application is a continuation application of Ser. No.10/038,575 filed Jan. 8, 2002, which claims the priority of the commonlyowned copending German patent application Serial No. 101 00 464.8 filedJan. 8, 2001. The disclosures of the aforementioned applications and ofeach US and foreign patent and patent application identified in thespecification of the present application are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] The invention relates to improvements in cutting or subdividingapparatus which employ replaceable cutting implements (hereinaftercalled knives for short). More particularly, the invention relates tomethods of and to apparatus for replacing worn, otherwise damaged and/orimproperly selected knives which are utilized to sever or subdividepartly finished (intermediate) products of the tobacco processingindustry. Examples of such intermediate products are continuouscigarette, cigar, cigarillo or other tobacco-containing rods andcontinuous rods containing fillers of filter material for tobacco smoke,tubes and other products which must be severed to respectively yieldplain cigarettes, filter mouthpieces or other products of unit length ormultiple unit length.

[0003] A cigarette making machine is designed to turn out at least onecontinuous rod-like product wherein a tubular wrapper of cigarette papersurrounds a rod-like filler of shredded and/or otherwise comminutedtobacco leaves and/or other smokable material. The apparatus (known ascutoff) which is utilized to subdivide the continuous rod-like productinto a file of discrete cigarettes of desired length comprises one ormore knives which severs or sever the rod-like product while advancingat the speed and in the direction of movement of the rod as well assideways across the path for the rod.

[0004] The quality of cuts across a continuously advancing cigarette rodis of considerable importance to the ultimate user because at least oneend of the finished cigarette is visible. Therefore, the cutting edge(s)of the knife or knives which is or which are used to subdivide acigarette rod is or are continuously sharpened whenever the cutoff is inuse. This results in pronounced wear upon the knives, and such weardevelops in addition to that which is attributable to sliding movementrelative to the advancing rod in actual use of the cigarette maker. Itis to be borne in mind that, in a modern cigarette making machine.(e.g., that known as PROTOS 2 and distributed by the assignee of thepresent application), a knife must carry out several thousand cuts perminute. The wear upon the knives is so pronounced that the cutoff mustreceive a new knife every eight hours or so.

[0005] At the present time, the removal of used knives and theirreplacement with fresh (new) knives are carried out by the attendants inthe cigarette making plant. This is a time-consuming operation,especially in a plant wherein several hundred machines are employed tosimultaneously turn out huge quantities of plain cigarettes of desiredlength. The situation is analogous in numerous plants which turn outcontinuous filter rods, continuous tubes intended to be subdivided intoshorter tubes for use in certain types of smokers' products, cigarillorods and many other rod-shaped intermediate (i.e., semifinished)products.

OBJECTS OF THE INVENTION

[0006] An object of the present invention is to provide a novel andimproved method which renders it possible to operate a cigarette makeror an analogous machine (such as a filter rod making machine) withconsiderable savings in man-hours.

[0007] Another object of the invention is to provide a method whicheliminates the need for manual replacement of spent and/or damagedand/or otherwise unsatisfactory knives in cigarette makers and analogousmachines with fresh knives.

[0008] A further object of the instant invention is to provide a methodwhich renders it possible to replace a spent knife in a cigarette makeror an analogous machine within a minute fraction of time which isnecessary to perform such work in accordance with presently knownproposals.

[0009] An additional object of the invention is to provide a novel andimproved method of manipulating spent knives and new knives in cigarettemakers and analogous machines which are designed to turn out continuoussmokers' products.

[0010] Still another object of the present invention is to provide anovel and improved apparatus for the practice of the above outlinedmethod.

[0011] A further object of this invention is to provide an apparatuswhich can be automated to any desired extent in a simple, time-savingand inexpensive but highly reliable manner.

[0012] Another object of the invention is to provide an apparatus whichcan be installed in or combined with existing machines serving to turnout cigarette rods, filter rods, cigarillo rods and analogousintermediate products of the tobacco processing industry.

[0013] An additional object of the invention is to provide a novel andimproved cutoff for use in cigarette makers and like or analogousmachines.

[0014] Still another object of the invention is to provide novel andimproved knife manipulating devices and groups of devices for use in theabove outlined apparatus and/or machines.

[0015] A further object of this invention is to provide a cigarettemaking, a cigar making, a filter rod making or an analogous machinewhich embodies or which is combinable with an apparatus of the aboveoutlined character.

SUMMARY OF THE INVENTION

[0016] One feature of the present invention resides in the provision ofa method of replacing an at least partially spent first knife (e.g., aknife which has undergone extensive wear), which is locked in the knifeholder of a severing unit (such as a cutoff) that is operative to seversmokers' products, with a second knife (e.g., with a new or freshknife). The improved method comprises the steps of automaticallyunlocking the first knife so that it is ready to be withdrawn orotherwise removed from the knife holder, removing the first knife fromthe holder, and introducing the second knife into the holder. Theremoving and/or the introducing step, too, can be performed by resortingto automatic equipment, and such automation of the severing unit can beeffected in addition to or in lieu of automation of the unlocking step.

[0017] The improved method can further comprise the step of engaging thefirst knife prior to the removing step, e.g., of clamping the firstknife by tongs or other suitable implements while the first knife isstill held in and biased and/or otherwise urged against the knifeholder. The removing step of such method can include advancing the firstknife along an at least substantially straight path, and such method canfurther comprise the step of delivering the removed first knife to andreleasing the first knife at a disposing station for spent knives. Theengaging step of the just discussed method can be carried out prior tothe unlocking step, and the removing step can include grasping thecutting edge or one of several cutting edges of the first knife.

[0018] The method can further comprise the step of moving the firstknife to a predetermined position relative to the knife holdersubsequent to the unlocking step and prior to completion of the removingstep. The latter can include placing a withdrawing unit for the firstknife opposite the first knife not later than when the first knifeoccupies the predetermined position.

[0019] The method can further comprise the step of interrupting theoperation of the severing unit at least in the course of the removingstep, and the step of maintaining the first knife at least close to apredetermined position at the time of initiation of the removing step.The removing step of such method can include placing a withdrawing unitfor the first knife opposite the first knife not later than when thefirst knife occupies the predetermined position.

[0020] If the method is being resorted to for replacement of a firstknife which is subject to wear during operation of the severing unit, itcan further comprise the steps of monitoring (e.g., optically and/orotherwise) the extent of wear upon the first knife during operation ofthe severing unit and initiating the removing step when the wear uponthe first knife reaches a predetermined value.

[0021] Still further, the method can comprise the step of automaticallylocking the second knife in the knife holder upon completion of theintroducing step.

[0022] The method can also comprise the steps of withdrawing the secondknife from a storage facility for second knives and conveying the thuswithdrawn second knife to a preselected position prior to theintroducing step. The conveying step of such method can include movingthe second knife along an at least partially linear path or along an atleast substantially linear path, and such method can further comprisethe step of transporting the knife holder to a position opposite thepreselected position of the second knife prior to the introducing step.

[0023] The operation of the severing unit can include or includes movingthe knife holder, and such method can further comprise the step ofinterrupting the step of moving the knife holder preparatory to and inthe course of the introducing step. Still further, such method cancomprise the steps of withdrawing the second knife from theaforementioned or from another storage facility, conveying the thuswithdrawn second knife to a preselected position prior to theintroducing step, and transporting the knife holder to a positionopposite the second knife in the preselected position of the secondknife.

[0024] The method can further comprise the step of locking the secondknife upon completion of the introducing step and/or the step ofmaintaining, at the time of initiation of the removing step, the knifeholder at least close to a predetermined position in which the secondknife can be introduced into the knife holder upon completion of theremoving step.

[0025] The method can include the step of automatically carrying out theremoving and/or the introducing step; such step of automaticallycarrying out at least one of the removing and introducing steps can beperformed by utilizing a computer. Furthermore, the aforementioned stepof automatically locking the second knife in the knife holder uponcompletion of the introducing step can be automated.

[0026] All in all, the heretofore discussed novel method can comprisethe step of automatically carrying out at least one of the followingadditional steps (the following listing of such steps is not exhaustive,i.e., the method can include one or more steps which can be utilized inlieu of or in addition to the listed steps):

[0027] Engaging the first knife prior to the removing step;

[0028] delivering the removed first knife to a disposing station forfirst knives (e.g., to a scrap collecting station);

[0029] moving the first knife to a predetermined position relative tothe knife holder subsequent to the unlocking step and prior tocompletion of the removing step;

[0030] interrupting the operation of the severing unit at least in thecourse of the removing step;

[0031] maintaining the first knife at least close to a predeterminedposition at the time of initiation of the removing step;

[0032] monitoring the extent of wear upon the first knife duringoperation of the severing unit;

[0033] initiating the removing step when the wear upon the first knifereaches a predetermined value;

[0034] locking the second knife in the holder upon completion of theintroducing step;

[0035] withdrawing the second knife from the aforementioned or anotherstorage facility for second knives;

[0036] conveying the withdrawn second knife to a predetermined positionprior to introduction of the second knife into the holder;

[0037] transporting the knife holder to a position opposite apreselected position of the second knife prior to the introducing step;

[0038] moving the knife holder during operation of the severing unit;

[0039] interrupting the movement of the knife holder preparatory to andin the course of the introducing step; and

[0040] maintaining—at the time of initiation of the removing step—theknife holder at least close to a predetermined position in which thesecond knife can be introduced into the knife holder upon completion ofthe removing step.

[0041] A modified method involves the removal of a knife which is lockedin the knife holder of a severing unit that is operative to seversmokers' products. This method comprises the steps of automaticallyunlocking the knife, and removing the unlocked knife from the knifeholder. Such method can further comprise the step of replacing theremoved knife with a second knife. At least one of the removing andreplacing steps can include advancing the respective knife along an atleast substantially linear path or along a path which includes at leastone linear portion, e.g., along a straight horizontal path.

[0042] A third method involves the introduction of a knife into theknife holder of a severing unit which is operative to sever smokers'products or the like. This method comprises the steps of conveying theknife into the knife holder, and automatically locking the conveyedknife in the knife holder. Such method can further comprise the step ofremoving a spent knife from the knife holder prior to the conveyingstep.

[0043] Another feature of the present invention resides in the provisionof an apparatus for replacing a first knife, which is locked in theknife holder of a severing unit in a machine for severing partlyfinished smokers' products, with a second knife. The improved apparatuscomprises disengageable means for locking the first knife in the holder,means for disengaging the locking means, means for removing the firstknife from the knife holder upon completed disengagement of the lockingmeans, and means for introducing the second knife into the knife holderupon removal of the first knife and prior to reengagement of the lockingmeans.

[0044] The locking means can comprise a biasing member (e.g., at leastone roller) that is movable between first and second positions in whicha knife is respectively locked in and removable from the knife holder,and the disengaging means of the apparatus can include a displacingmember as well as means for moving the displacing member relative to theknife holder to thus move the biasing member from the first position tothe second position, at least during removal of the first knife from theknife holder. The displacing member can include a reciprocable bolt, andthe removing means can include means for clamping the first knife atleast during removal of such knife from the knife holder. Such clampingmeans can be arranged to clamp the cutting edge of the first knifeduring removal of this knife from the knife holder.

[0045] The removing means can further comprise means for moving theclamping means and the first knife along an at least partially linearpath which extends away from the knife holder.

[0046] The improved apparatus can further comprise means for engagingthe locking means upon introduction of the second knife into the knifeholder; such engaging means can include the disengaging means or viceversa.

[0047] If the locking means comprises the aforementioned biasing member,the apparatus can further comprise means for moving the biasing memberbetween its aforementioned first and second positions and means forconveying the second knife into the knife holder in the second positionof the biasing member and upon removal of the first knife from the knifeholder. Such apparatus can further comprise a storage facility for asupply of second knives, and the conveying means of such apparatus isthen arranged to move discrete second knives seriatim from the storagefaciliy to the knife holder. Such conveying means can comprise drivenrollers which are arranged to advance second knives from the storagefacility to the knife holder. The storage facility can compriseresilient means for biasing second knives of the supply of second knivesin the storage facility against each other.

[0048] The disengaging means can include means for releasably locking asecond knife in the knife holder upon introduction of such second knifeinto the holder.

[0049] A modified apparatus can be utilized for the withdrawal of an atleast partially used and/or damaged knife which is lockingly engaged bythe knife holder of a machine for severing partly finished smokers'products. This apparatus comprises means for terminating the lockingengagement between the knife and the holder, and means for removing theknife from the knife holder upon termination of the locking engagement.Such apparatus can further comprise means for introducing a fresh knifeinto the knife holder upon removal of the at least partially used and/ordamaged knife.

[0050] A further apparatus can be utilized for insertion of a knife intothe knife holder of a machine for severing partly finished smokers'products. This apparatus comprises means for releasably locking knivesin the holder, means for disengaging the locking means, and means forconveying discrete knives into the knife holder in the disengagedcondition of the locking means. This apparatus preferably furthercomprises a source of knives and its conveying means is or can bearranged to transport discrete knives from the source to the knifeholder. The locking means can comprise means for clamping knives to theknife holder.

[0051] The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved apparatus itself, however, both as to its construction and themodes of assembling and operating the same, together with numerousadditional important and advantageous features and attributes thereof,will be best understood upon perusal of the following detaileddescription of certain presently preferred specific embodiments withreference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

[0052]FIG. 1 is a partly plan and partly horizontal sectional view of anapparatus which is arranged to at least partly automatically replacespent knives with fresh knives in the cutoff of a cigarette makingmachine;

[0053]FIG. 2 is a partly elevational and partly vertical sectional viewof the apparatus which is shown in FIG. 1; and

[0054]FIG. 3 is a flow diagram wherein the characters denote varioussteps of a series of steps in a method embodying one form of theinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0055] The apparatus 1 which is shown in FIGS. 1 and 2 serves to replacesuccessive first knives 2 with successive second or new or fresh knives.The knife 2 which is shown in FIGS. 1 and 2 is in use or is alreadyspent (worn) to such an extent that it is advisable to replace it with asecond knife 6. To this end, the apparatus 1 is designed to deactivate alocking device 16 which serves to releasably hold the knife 2 in theholder 4 of a cutting or severing unit 12 (hereinafter called cutoff).The later is assumed to be installed in or on the housing 10 of acigarette rod making machine wherein the continuously produced cigaretterod advances lengthwise in a direction at right angles to the cuttingedge 14 of the knife 2 and at right angles to the plane of FIG. 1. Uponremoval from the holder 4, the knife 2 is delivered to a collectingstation, e.g., to a scrap gathering unit (not shown), and is replacedwith the foremost fresh knife 6 which must be withdrawn from a storagefacility 8.

[0056] The cutoff 12 comprises a drum 11 which is driven to rotate at ahigh speed related to the speed of forward movement of the continuouscigarette rod in such a way that the rod is subdivided into a file ofsuccessive coaxial plain cigarettes of say double unit length. Suitablecutoffs are disclosed, for example, in U.S. Pat. No. 3,140,632 (grantedJul. 14, 1964 to Rowlands et al.), U.S. Pat. No. 3,476,002 (granted Nov.4, 1969 to Bardenhagen et al.), U.S. Pat. No. 3,815,460 (granted Jun.11, 1974 to Bardenhagen) and U.S. Pat. No. 3,830,126 (granted Aug. 20,1974 to Ringe), as well as in German patent No. 38 35 314 C2.

[0057] The locking device 16 comprises a roller 18 movable between afirst position in which it biases the knife 2 against the holder 4, anda second position in which the knife 2 is removable from the holderpreparatory to introduction of a fresh knife. The shaft 20 of the roller18 is guided in a channel 24 which extends at an acute angle to thesurface 22 of the knife; this shaft is biased by a prestressed spring 26which serves to urge the shaft 20 in a direction to bias the roller 18against the surface 22 of the knife 2. Thus, the knife 2 is clampedbetween the roller 18 and a second roller 28 which serves as astationary stop and is operatively connected with a feed screw 31 by anangular drive 29. When the feed screw 31 is rotated, the roller 28 iscaused to turn and to move the knife 2 relative to the holder 4 to anextent which is necessary to compensate for wear at the cutting edge 14of the knife. This ensures that the cutting edge is maintained in anoptimum position for repeatedly severing the running cigarette rod. Themeans for grinding (sharpening) the knife 2 is not shown in FIGS. 1 and2.

[0058] The apparatus 1 cooperates with the severing unit 12; thisapparatus comprises a base plate or support 30 which is secured to aportion 34 of the housing 10 of the cigarette maker by means of aplate-like connector 32. The connector 32 is movable (with the support30) linearly along a straight path in directions which are indicated bythe double-headed arrow 36. This arrow is further intended to representa drive which is employed to move the parts 30, 32 in directions towardand away from the cutoff 12.

[0059] The support 30 of the apparatus 1 carries an unlocking ordisengaging unit 38 which serves to effect a disengagement of the knife2 from the holder 4, preferably at a time when the second (fresh) knife6 is ready to be introduced into the knife holder 4. The unlocking unit38 comprises a bolt-shaped displacing member 42 and acylinder-and-piston unit 40 which is affixed (e.g., bolted) to thesupport 30 and serves to move the displacing member 42 relative to theholder 4. A guide 44 is provided to establish an at least substantiallystraight path for movements of the displacing member 42. The latter canbe moved to a predetermined or preselected position in which it islocated directly opposite an opening 46 in the surface 48 of the housing10 for the severing unit 12. When it assumes its fully extendedposition, the member 42 can act upon the shaft 20 for the roller 18 insuch a way that the roller 18 is urged against the knife 2 by overcomingthe opposition of the spring 26, i.e., the shaft 20 is moved(rearwardly) in the channel 24 so that the knife 2 is no longer clampedbetween the rollers 18 and 28.

[0060] The apparatus 1 further comprises a unit 50 which serves as ameans for removing or withdrawing the knife 2 from the holder 4. Thisremoving unit includes a clamping lever 52 which is pivotable by afluid-operated cylinder 51 to turn about the axis of a shaft 54. A sideor surface 56 of the clamping lever 52 confronts the guide 44 andcooperates with this guide to clamp the cutting edge 14 of the knife 2(see FIG. 1). Such clamping action is produced in response to outwardmovement of the piston rod of the cylinder 51 and the resulting pivotingof the clamping lever 52 of the withdrawing unit 50 about the axis ofthe shaft 54.

[0061] The support 30 further carries a conveyor 60 which serves as atransporting unit for introduction of a new knife 6 from the storagefacility 8 into the knife holder 4. The storage facility 8 containssprings 62 (FIG. 1 shows coil springs) which urge the fresh knives 6 ofa stack or another suitable accumulation of such knives against eachother in that the springs bias a platform-like member 64. The latterurges the nearest knife 6 in a direction to maintain the foremost knife6 of the stack in the storage facility 8 in contact with rotary backsupports 66 (see particularly FIG. 2).

[0062] The conveyor 60 includes rollers 68 and 72 which can be driven bya prime mover 70 to advance the foremost knife 6 of a stack of suchknives in the storage facility 8 toward the knife holder 4. The rollers68 and 72 are rotatable about parallel axes and are respectivelyinstalled between a front set and a rear set of rotary back supports 66and in front of the left-hand back supports.

[0063] The roller 72 is or can be driven by the prime mover 70 (e.g., anelectric motor) which further serves to drive the composite roller 68.The distance between the axes of the rollers 68 and 72 is somewhat lessthan the length of a knife 2 or 6; this ensures that the knife 6 whichis to be introduced into the holder 4 is continuously guided, i.e., allthe way from the storage facility 8 to the point of its entry into theknife holder 4.

[0064]FIG. 2 shows numerous components of the cutoff 12 and of the knifechanging apparatus 1, as well as two endless belts, bands or chains 80,82 which respectively serve to transmit motion from the prime mover 70to the rollers 68 and 72.

[0065] The diagram of FIG. 3 is a pictorial representation of the stepswhich can be carried out in accordance with certain presently preferredembodiments of the improved method. The method includes the steps whichare carried out in order to replace a worn or damaged or improperlyselected first knife 2 (hereinafter called used knife) with a secondknife 6 (hereinafter called new knife). The method is carried out byresorting to the combination of a cigarette making machine employing acutoff 12 and a knife changing apparatus 1. The cigarette making machinecan be of the type disclosed in U.S. Pat. No. 4,281,670 granted Aug. 4,1981 to Heitmann et al. wherein FIG. 1 shows a cutoff 94. However, it isalso possible to employ the apparatus 1 in combination with anothermachine which turns out one or more semfinished products (such as acontinuous filter rod) and subdivides the semifinished product(s) intoone or more files of discrete rod-shaped ultimate products such asfilter mouthpieces of unit length or multiple unit length. Reference maybe had to U.S. Pat. No. 4,412,505 granted Nov. 1, 1983 to Häusler et al.wherein a continuous filter rod containing a filter tow confined in atubular wrapper is repeatedly severed by a cutoff 26.

[0066] The slogans which are utilized in the diagram of FIG. 3 areintended to facilitate the understanding of functions of variousdevices, instrumentalities, discrete parts and other constituents whichare shown, at least in part, in FIGS. 1 and 2 and which are or which canbe employed to carry out the steps of the improved method(s).

[0067] The step A denotes completion of movement of certain mobile partsof the conveyor 60 of the apparatus 1, and more particularly the(starting) positions such parts assume when the foremost new knife 6 ofthe stack in the storage facility 8 is remote from the knife holder 4 ofthe cutoff 12. A trailing or rear edge face 33 of the connector 32 abutsan end portion 35 of the housing 34 of the cigarette rod making machineincluding the cutoff 12.

[0068] Upon elapse of an interval between the step or assumption ofcondition denoted by A and the step or condition depicted at Aa, asensor or counter 90 (FIG. 2) which is a part of or cooperates with acomputerized control circuit 92 transmits to the latter a signaldenoting that the extent of wear upon the cutting edge 14 of the knife 2clamped in the holder 4 is sufficient to warrant replacement of suchknife with a new knife 6. The sensor 90 can be designed to transmit tothe control circuit 92 a signal when the number of incremental forwardmovements of the knife 2 in the holder 4 (in order to compensate forwear upon the cutting edge 14 of such knife) reaches a predeterminedupper limit.

[0069] The next step (shown at B and caused by the control circuit 92 inresponse to a signal from the sensor 90) involves a movement (see thearrow 36) of certain parts of the apparatus 1 from starting positions topositions in which the new knife 6 is delivered linearly into closeproximity of the cutoff 12 (this is the knife detecting position of suchmobile parts of the conveyor 60). The sensor 90 (e.g., a photoelectronicdetector) can detect the used knife 2 in the holder 4. Thus, the sensor90 can count the number of successive incremental advances of the knife2 as well as or actually detect the knife 2 in the holder 4 uponadvancement of such sensor to the knife holder.

[0070] The cutoff 12 is arrested (see the step B) in that angularposition of the drum 11 for the used knife 2 in which this knife ismaintained in or close to a predetermined angular position relative tothe axis of the drum 11. The cigarette making machine including thecutoff 12 is arrested (step B) as soon as the used knife 2 reaches itspredetermined position.

[0071] In the next step, the spent knife 2 is gradually (slowly) movedto a position which is an optimum position for the next-following stepsof the method. Such optimum position of the spent knife 2 is indicatedat Ba.

[0072] The mobile parts of the knife changing apparatus 1 thereuponrenew their movement in the direction of the arrow 36 to assume (at C)loading or transfer positions close to the used knife 2. At such time,the connector 32 and the aparatus 1 are located in the (loading ortransferring) positions shown in FIG. 1 (step Ca in the diagram of FIG.3).

[0073] The next step (D) involves an activation of thecylinder-and-piston unit 40 so that the bolt 42 releases the knife 2 bycausing a disengagement of the locking device 16. This is achieved bymoving the roller 18 away from the roll 28. The next step (Da) involvesthe generation (by the sensor 90 or by a discrete second sensor) of asignal denoting that the knife 2 is still in the holder 4.

[0074] The character E denotes the step of activating the removing unit50 which then causes the surface 56 of the lever 52 and the guide 44 ofthe unlocking unit 38 to clamp the knife 2. The sensor 90 or anadditional sensor can be utilized (see the step Ea) to ascertain whetheror not the knife 2 is still clamped. If the answer is in theaffirmative, the next-following step (F) involves a return movement ofthe apparatus 1 to its starting or retracted position, i.e., to aposition remote from the cutoff 12.

[0075] The step denoted by the symbol Fa indicates a determinationwhether or not the apparatus 1 has reassumed its starting position andthe knife 2 is still held in the holder 4. The next-following step Gthen involves a determination of clamping action by the withdrawing unit50. The step Ga includes ascertaining whether or not the unit 50 isinactive. In the next step, the conveyor 68 (and particularly itstransporting roller 72) advances the knife 2 through a short distancetoward the cutoff 12 so that it can leave the apparatus. A furthersensor (such as the sensor 94 shown in FIG. 1) can be employed toascertain and to preferably indicate whether or not the spent knife 2has left the apparatus 1.

[0076] If the answer denoted by the signal from the sensor 94 is in theaffirmative, the apparatus 1 carries out the step C, i.e., it reassumesthe position close to the cutoff 12 to deliver the foremost new knife 6into the holder 4 (see FIG. 1). The step Ca (which follows the step C)follows a determination whether or not the apparatus 1 is actually heldin the loading position. The roll 18 is thereupon actuated by the bolt42 to open (step D) the holder 4 for entry of the fresh knife 6.

[0077] The next step (Db) involves a determination (by the sensor 90 or94 or a further sensor) whether or not a knife is then located in theholder 4. The bolt 42 continues to hold the roller 18 in the idleposition, and the next step (shown at H) includes starting the primemover 70 to drive the rollers 68 and 72, i.e., to move the fresh knife 6from the storage facility and entirely into the empty holder 4.

[0078] The step Ha involves the utilization of a sensor (i.e., of thesensor 90 or 94 or a further sensor) to ascertain whether or not the newknife 6 is properly received in the holder 4. If the answer is in theaffirmative, the next step (Fb) involves a return (renewed) movement ofthe apparatus 1 to its starting position A, the sensor 90 is reset tozero, the sensor which monitors the evacuation of used knife 2 from thecutoff 12 is also reset to zero, and the cigarette making machine andits cutoff 12 are restarted.

[0079] The new knife 6 is preferably inserted into the holder 4 in sucha way that the sharpening or grinding unit for the cutting edge of suchknife is immediately ready to undergo the necessary sharpening treatmentat a rate corresponding to the extent of wear when the cutoff 12 is inuse.

[0080] An important advantage of the improved method is that one or moresteps can be performed automatically. This contributes significantly tosavings in workers' time and renders it possible to carry out all or allimportant or all tedious or all time-consuming operations or steps byresorting to automated equipment. As already mentioned hereinbefore,savings in time in connection with the retooling or refitting of cutoffsare particularly important when a plant employing numerous cigarettemaking, filter rod making or analogous machines must be equipped withfresh cutting implements at frequent intervals such as upon completionof each eight-hour shift.

[0081] It has been found that the improved apparatus can be automated tosuch an extent that spent (used) knives can be replaced with new kniveswithout necessitating any work by the attendants. In fact, a singleattendant can supervise the operation of entire batteries of cigarettemaking and analogous machines, at least insofar as the replacement ofused knives is concerned. Such single attendant is called upon tointerfere only and alone in the event of a malfunction or anotherunforeseen occurrence.

[0082] A step which is presently considered as being particularlyimportant in connection with the automation of knife changes is that ofautomatically unlocking a knife 2 which is installed in the holder 4.Another important step is that which involves automatic positioning ofthe foremost new knife 6 for transport toward and for holding at thecutoff 12 prior to removal of the used knife. The locking device 16 canbe used to lock a knife 2 in the holder 4 as well as to lock eachfollowing knife 6 in such holder. It has been ascertained that theautomation of operation of the locking device 16 contributessignificantly to facilitation of automation of numerous or all othersteps including monitoring the condition of the knife 2 in the holder 4,disengaging the locking device 16, withdrawing a spent knife 2 from theopened holder 4, introducing a new knife 6 into the holder 4, andthereupon locking (such as clamping) the newly introduced knife 2 in theholder.

[0083] An advantage of the feature that the withdrawing unit 50 is setup to engage the cutting edge 14 of a knife prior to withdrawal of such(spent) knife from the holder 4 is that the cutting edge of such knifeis or can be expected to be readily available from the outside forclamping and extraction from the holder.

[0084] The feature that a knife is maintained in a first predeterminedposition when the cutoff is brought to a halt, and that the knife isthereupon slowly moved to a second predetermined position is ofparticular advantage in machines (such as cigarette makers) which aredesigned to turn out huge quantities of discrete rod-shaped products perunit of time. Thus, the knife 2 in the cutoff 12 of a cigarette maker isdecelerated from the normal operating speed to a much lower speed in thefirst step, and the knife is thereupon brought to a complete stop in thenext-following step. When the knife 2 is brought to a halt, it is in anoptimum position for extraction from the holder 4 by the withdrawingunit 50.

[0085] An advantage of the feature that the extent of wear upon theknife 2 in the holder 4 is monitored (directly by ascertaining thecondition of the cutting edge 14 and/or indirectly by monitoring thenumber of severing operations being carried out by the knife) is that aknife is discarded only when it is no longer satisfactory for acceptablesevering of cigarette rods, filter rods and the like. The simplestpresently known monitoring device for the condition of a knife in theknife holder of a cutoff in a cigarette maker is a revolution counterwhich ascertains the number of revolutions of the drum 11 or of theknife in its holder or of any other rotary part of the cutoff.

[0086] The conveyor 60 exhibits the important advantage that it canenter a new knife 6 into the knife holder 4 in several stages. Thisensures that the foremost new knife can be moved close to the cutoffwhile the previous knife (2) is still in use, and that the final stageof transfer of the new knife into the holder 4 can take place withlittle loss in time and as soon as the used knife is evacuated by thewithdrawing unit 50. The first stage of movement of a new knife 6 fromthe storage facility 8 is or can be carried out by moving the knife 6along a linear-or at least substantially straight path. Such first stageof movement is preferably terminated when the new knife is in close orimmediate proximity to the cutoff 12, as long as it does not interferewith withdrawal and evacuation of the used knife. The two (or more)stages of conveying a new knife 6 to the holder 4 can be carried outimmediately after each other so that such introduction of the new knifeinto the holder takes up a suprisingly short interval of time.

[0087] The second stage of movement of a new knife 6 toward the holder 4can be carried out at a speed which is less or much less than the speedof the first stage of such movement; this contributes to greateraccuracy of positioning of the new knife prior to actual introductioninto the cutoff 12. Moreover, such selection of the speeds of first andsecond stages of conveying of a new knife to the holder 4 renders itpossible to take into consideration the elevated speeds of rotary knivesin cigarette making and analogous mass-producing machines or productionlines for the making of smokers' products. In accordance with apresently preferred embodiment, the holder 4 remains open from theinstant of initial withdrawal of a used knife 2 (i.e., from the instantof deactivation of the locking device 16) to the instant of insertion ofthe new knife into and of its locking in the knife holder. Also, theposition of the knife holder with reference to the stationary part orparts of the cutoff 12 need not be changed for withdrawal of a usedknife and/or for subsequent insertion of a new knife.

[0088] It is presently preferred to employ the unlocking device 38 inconnection with manipulation of the locking device 16 to release a usedknife as well as to lock a new knife in the knife holder. Thiscontributes to significant savings in space requirements and initial andmaintenance cost of the apparatus 1.

[0089] Without further analysis, the foregoing will so fully reveal thegist of the present invention that others can, by applying currentknowledge, readily adapt it for various applications without omittingfeatures that, from the standpoint of prior art, fairly constituteessential characteristics of the generic and specific aspects of theabove outlined contribution to the art of replacing knives and/or othercutting implements in cut-offs and other severing machines and,therefore, such adaptations should and are intended to be comprehendedwithin the meaning and range of equivalence of the appended claims.

What is claimed is:
 1. A method of replacing an at least partially spentfirst knife, which is locked in the knife holder of a severing unit thatis operative to sever smokers' products, with a second knife, comprisingthe steps of: moving the first knife relative to the holder;automatically unlocking the first knife; removing the first knife fromthe holder; and introducing the second knife into the holder.
 2. Themethod of claim 1, further comprising the step of engaging the firstknife prior to said removing step, said removing step includingadvancing the first knife along an at least substantially straight pathand further comprising the step of delivering the removed first knife toand releasing the first knife at a disposing station for spent knives.3. The method of claim 2, wherein said engaging step is carried outprior to said unlocking step.
 4. The method of claim 2 of replacing afirst knife having a cutting edge, wherein said removing step furtherincludes grasping the cutting edge of the first knife.
 5. The method ofclaim 1, further comprising the step of moving the first knife to apredetermined position relative to the holder subsequent to saidunlocking step and prior to completion of said removing step.
 6. Themethod of claim 5, wherein said removing step includes placing awithdrawing unit for the first knife opposite the first knife not laterthan when the first knife occupies said predetermined position.
 7. Themethod of claim 1, further comprising the step of interrupting theoperation of the severing unit at least in the course of said removingstep.
 8. The method of claim 7, further comprising the step ofmaintaining the first knife at least close to a predetermined positionat the time of initiation of said removing step.
 9. The method of claim8, wherein said removing step includes placing a withdrawing unit forthe first knife opposite the first knife not later than when the firstknife occupies said predetermined position.
 10. The method of claim 1 ofreplacing a first knife which is subject to wear during operation of thesevering unit, further comprising the steps of monitoring the extent ofwear upon the first knife during operation of the severing unit andinitiating said removing step when the wear upon the first knife reachesa predetermined value.
 11. The method of claim 1, further comprising thestep of automatically locking the second knife in the holder uponcompletion of said introducing step.
 12. The method of claim 1, furthercomprising the steps of withdrawing the second knife from a storagefacility for second knives and conveying the thus withdrawn second knifeto a preselected position prior to said introducing step.
 13. The methodof claim 12, wherein said conveying step includes moving the secondknife along an at least partially linear path.
 14. The method of claim12, wherein said conveying step includes moving the second knife alongan at least substantially linear path.
 15. The method of claim 12,further comprising the step of transporting the knife holder to aposition opposite said preselected position of the second knife prior tosaid introducing step.
 16. The method of claim 1, wherein the operationof the severing unit includes moving the knife holder and furthercomprising the step of interrupting the moving step preparatory to andin the course of said introducing step.
 17. The method of claim 16,further comprising the steps of withdrawing the second knife from astorage facility, conveying the thus withdrawn second knife to apreselected position prior to said introducing step, and transportingthe knife holder to a position opposite the second knife in thepreselected position of the second knife.
 18. The method of claim 1,further comprising the step of locking the second knife in the knifeholder upon completion of said introducing step.
 19. The method of claim1, further comprising the step of maintaining, at the time of initiationof said removing step, the knife holder at least close to apredetermined position in which the second knife can be introduced intothe knife holder upon completion of said removing step.
 20. The methodof claim 1, further comprising the step of automatically carrying out atleast one of said removing and introducing steps.
 21. The method ofclaim 20, wherein said step of automatically carrying out at least oneof said removing and introducing steps is computerized.
 22. The methodof claim 1, further comprising the step of automatically locking thesecond knife in the holder upon completion of said introducing step. 23.The method of claim 1, further comprising the step of automaticallycarrying out at least one of additional steps including: engaging thefirst knife prior to said removing step, delivering the removed firstknife to a disposing station for first knives, moving the first knife toa predetermined position relative to the holder subsequent to saidunlocking step and prior to completion of said removing step,interrupting the operation of the severing unit at least in the courseof said removing step, maintaining the first knife at least close to apredetermined position at the time of initiation of said removing step,monitoring the extent of wear upon the first knife during operation ofthe severing unit, initiating the removing step when the wear upon thefirst knife reaches a predetermined value, locking the second knife inthe holder upon completion of said introducing step, withdrawing thesecond knife from a storage facility for second knives, conveying thewithdrawn second knife to a predetermined position prior to saidintroducing step, transporting the knife holder to a position opposite apreselected position of the second knife prior to said introducing step,moving the knife holder during operation of the severing unit,interrupting the movement of the knife holder preparatory to and in thecourse of said introducing step, and maintaining—at the time ofinitiation of said removing step—the knife holder at least close to apredetermined position in which the second knife can be introduced intothe knife holder upon completion of said removing step.
 24. Apparatusfor replacing a first knife, which is locked in a knife holder of asevering unit in a machine for severing partly finished smokers'products, with a second knife, comprising: means for moving the firstknife relative to the holder; disengageable means for locking the firstknife in the holder; means for disengaging said locking means; means forremoving the first knife from the holder upon disengagement of saidlocking means; and means for introducing the second knife into theholder upon removal of the first knife prior to reengagement of thelocking means.
 25. The apparatus of claim 24, wherein said locking meanscomprises a biasing member movable between first and second positions inwhich a knife is respectively locked in and removable from the holder,said disengaging means comprising a displacing member and means formoving said displacing member relative to the holder to thus move saidbiasing member from said first to said second position thereof at leastduring removal of the first knife from the holder.
 26. The apparatus ofclaim 25, wherein said biasing member comprises at least one roller andsaid displacing member comprises a reciprocable bolt.
 27. The apparatusof claim 24, wherein said removing means includes means for clamping thefirst knife at least during removal of the first knife from the holder.28. The apparatus of claim 24 for replacing a first knife having acutting edge, wherein said removing means comprises means for clampingthe cutting edge of the first knife during removal of the first knifefrom the holder.
 29. The apparatus of claim 28, wherein said removingmeans further comprises means for moving said clamping means and thefirst knife along an at least partially linear path extending away fromthe holder.
 30. The apparatus of claim 24, further comprising means forengaging said locking means upon introduction of the second knife intothe holder.
 31. The apparatus of claim 30, wherein said engaging meansincludes said disengaging means.
 32. The apparatus of claim 24, whereinsaid locking means comprises a biasing member movable between first andsecond positions in which a knife is respectively locked in andremovable from the holder, and further comprising means for moving thebiasing member between said positions and means for conveying the secondknife into the holder in the second position of said biasing member andupon removal of the first knife from the holder.
 33. The apparatus ofclaim 32, further comprising a storage facility for a supply of secondknives, said conveying means being arranged to move discrete secondknives seriatim from said storage facility to the holder.
 34. Theapparatus of claim 33, wherein said conveying means comprises drivenrollers arranged to advance second knives from said storage facility tothe holder.
 35. The apparatus of claim 33, wherein said storage facilitycomprises resilient means for biasing second knives of the supplyagainst each other.
 36. The apparatus of claim 24, wherein saiddisengaging means includes means for releasably locking a second knifein the holder upon introduction of such second knife into the holder.37. A method of removing a knife which is locked in the knife holder ofa severing unit that is operative to sever smokers' products, comprisingthe steps of: moving the knife relative to the holder; automaticallyunlocking the knife; and removing the unlocked knife from the holder.38. The method of claim 37, further comprising the step of replacing theremoved knife with a second knife.
 39. The method of claim 38, whereinat least one of said removing and replacing steps includes advancing therespective knife along an at least substantially linear path.
 40. Amethod of introducing a knife into the knife holder of a severing unitwhich is operative to sever smokers' products, comprising the steps of:conveying the knife into the knife holder; automatically locking theconveyed knife in the knife holder; and moving the knife relative to theholder.
 41. The method of claim 40, further comprising the step ofremoving a spent knife from the holder prior to said conveying step. 42.Apparatus for withdrawing an at least partially used and/or damagedknife which is lockingly engaged by the knife holder of a machine forsevering partly finished smokers' products, comprising; means for movingthe knife relative to the holder; means for terminating the lockingengagement between the knife and the holder; and means for removing theknife from the knife holder upon termination of said locking engagement.43. The apparatus of claim 42, further comprising means for introducinga fresh knife into the knife holder upon removal of the at leastpartially used and/or damaged knife.
 44. Apparatus for inserting a knifeinto the knife holder of a machine for severing partly finished smokers'products, comprising: means for releasably locking knives in the holder;means for disengaging said locking means; means for conveying discreteknives into the holder in the disengaged condition of said lockingmeans; and means for moving the knife relative to the holder.
 45. Theapparatus of claim 44, further comprising a source of knives, saidconveying means being arranged to transport discrete knives from saidsource to the holder.
 46. The apparatus of claim 44, wherein saidlocking means includes means for clamping knives to the holder.